1. Field of Invention
The invention relates to bar clamps and more particularly to an improved lock mechanism for a bar clamp.
2. Description of Related Art
A typical lock mechanism for a bar clamp is shown in FIGS. 1, 2A and 2B. The slide bar comprises a slide bar 10 of rectangular longitudinal section including a through hole 11 of circular section, a housing with a moveable jaw carrier 12 integrally formed therewith, the moveable jaw carrier 12 having a channel 121 therethrough; a knob shaped slide member 20 including a rod 21 secured to an inner surface, the slide member 20 being slidably retained in a recess on one surface of the moveable jaw carrier 12 with the rod 21 also slidably disposed in the recess and the through hole 11; and a push button 30 including a shaft 31 extending from an inner surface, and a helical spring 32 put on the shaft 31, the push button 30 slidably retained in a recess on the other opposite surface of the moveable jaw carrier 12. The shaft 31, the through hole 11, and the rod 21 are aligned.
In a locked position, the rod 21 is partially disposed in the through hole 11 to lock the moveable jaw carrier 12 (see FIG. 2A). For unlocking the moveable jaw carrier 12, a user may push the push button 30 to cause the shaft 31 to push the rod 21 with the spring 32 being compressed until the rod 21 completely leaves the through hole 11 (see FIG. 2B).
However, the rod 21 may enter or leave the through hole 11 without force being exerted upon the slide member 20 after a period of time of use. This is because the sliding nature of the slide member 20 and wear. As a result, the desired reliable locking function is compromised. Thus, the need for improvement still exists.